ry to the existence of all
life, and to all physical change in the universe. Mayer showed us that
all energy in the solar system primarily derives its existence from the
sun, and that all plant life and physical life owe their continued
existence to the energy which is poured out from the sun upon the
planetary worlds. So that energy is always flowing from the sun into the
surrounding space in the form of light, heat, and electricity, the
medium of its passage being the universal Aether.

This principle of transformation teaches us, that heat may be converted
into electricity; that light may be converted into heat, or electricity
may be converted into either heat or light or both. This principle of
transformation naturally follows from the principle of the conservation
of energy; because, if energy cannot be destroyed in any way, but is
made to disappear by any process, it must reappear in some other form,
and therefore has been transformed from its original state. So that,
whenever one kind of energy disappears, then it is absolutely necessary,
according to the principle of conservation of energy, that some other
kind shall be produced. There cannot be any real loss or destruction.

That leads us to the next point regarding this principle of
transformation, which is that all transformations of energy take place
in fixed proportions. When a certain quantity of coal is burned, a
certain quantity of heat, or thermal energy as it is sometimes called,
is produced, and the quantity of heat so produced is definitely
proportionate to the quantity of coal consumed.

If a certain quantity of coal were burned in a perfect steam-engine,
that is one in which there would be no loss of heat, then also a
definite amount of mechanical work would be done, which would be
strictly proportionate to the heat generated by the consumption of the
coal. So that when coal is put into an engine, the potential energy of
the coal is transformed into kinetic energy of the steam, and that is
again transformed into actual mechanical energy of the engine itself, by
which work is done in driving or pushing or pulling the train along, and
the amount of work done is proportionate to the coal consumed.
Illustrations of transformation are common, and may be seen by any
person living in a large town. Thus at any electrical station or
electric tram terminus, these transformations of various forms of energy
are very familiar sights. We have first the transfo